Due to the high temperature of a metal strand emerging from a continuous chill mould, the guide rollers of a continuous casting installation are cooled with cooling water which is centrally supplied to and removed from a distribution system provided in each guide roller via a rotary transmission leadthrough at one or both ends of the guide roller. Since during operation the guide rollers sag and also expand axially, the rotary transmission leadthroughs disposed at the ends of the water-cooled guide rollers are subjected to considerable mechanical loadings which necessitate the stoppage of the continuous casting installation after a relatively short period of service and the replacement of the rotary transmission leadthroughs.
Another disadvantage of the prior art continuous casting installations is that the guide rollers are mounted with their bearing pins in open bearings which must be regularly lubricated. Quite apart from the fact that this causes considerable consumption of lubricant, the bearings are also liable to dirtying and therefore wear, so that they also must be periodically replaced, something which can be done only during a stoppage of the continuous casting installation.
For a long time efforts have been made to eliminate these defects. In a rotary transmission leadthrough which has just become known the bearing pin of the guide roller with its bearing is covered at the end by a cover plate borne by the bearing block of the guide roller. Furthermore, disposed between the cover plate and the bearing pin is a seal which consists of a bush axially moveable and rotatably and covered in a central bore of the cover plate, a flange connected sealing-tight and non-rotatably to the bearing pin, and a flexible sealing connecting member disposed between the bush and the flange, the flexible connecting member taking the form of tubular metal bellows and being disposed in a tubular attachment of the flange. The diameter of the central channel of the distributing system in the bearing pin is increased to accommodate the said attachment with the bellows. Such a rotary transmission leadthrough ensures on the one hand that the bearing is protected against dirtying from outside on one side by the cover plate in conjunction with the special seal and no water can get into the bearing, while on the other hand the rotary transmission leadthrough is not loaded by mechanical forces generated by the sagging of the guide roller and its axial expansion. These advantages result in a prolonged service life of the rotary transmission leadthrough and the bearing. However, it is a disadvantage that the seal operative between the cover plate and the bearing pin is of a very expensive design.